Frequency-dividing system



Nov. 12, 1940. H, LEMS i 2,221,452

FREQUENCY-DIVIDING SYSTEM Filed Dec. 15. 1938 l M PULSE GENERATOR Ouihodo PIC-3.2

2 INVENTOR D M. LEWIS ATI'ORNEY Patented Nov. 12, t

" uN TEo STATES PATENT OFFICE assists mQUaNcr-mvmmo srs'rlm Harold M. Lewis, Great Neck, N. Y., assignor to Hazeltine Corporation, a corporation of Bob Application ntcemt i- 1a, 1938, serial No. 245354 a clams. (.01. 250- 38) This invention relates to frequency-dividing systems for deriving from one periodic wave of a first predetermined frequency another periodic wave of a second predeterminedfrequency which 5 is a submultiple of the first frequency. M Devices of this character are. particularly usefulin television systems where waves of various diflerent frequencies bearing a constant frequency relation to each other are utilized. For example,

2 It is an object of the present invention, therefore, to provide an improved frequency-dividing system e'mbodyingthe essential features mentioned above. a v

In accordance with the present invention, there 25 is provided a frequency-dividing system which comprises an input circuit adapted to be energized. by aperiodic wave of a predetermined frequency.

'by-thesystemlls g Referring in detail to frequency-dividing system II, this system comprises an input. circuit 80 The frequency divider also includes energy-storage means, for example,- acondenser, together 80 with means for effecting charging of the storage means only upon its discharge to a predetermined value. Discharging means are coupled to the energy-storage means and to the input circuit so as to operate only in response to, and during 85 pulses of, the periodic-input wave, incrementally and periodically to discharge the eni'argy-storage means at the predetermined frequency and to such an extent that a predetermined'number of the incremental discharges are required to effect 40 initiation of the charging of the energy-storage means. The discharge means may comprise-a diode connected in series with the energy-storage means together with meansfor biasing the diode to render it normally nonconducting and means 46 for coupling the diode to the input circuit so that the application ofthe periodic wave thereto pe'riodically overcomes the bias to effect the incremental and periodic discharges of the energy storage means. The system includes an output 50 circuit responsive to the successive chargings of the energy-storagemeans'. In accordance with a feature of the invention, the charging means for effectively charging the energy-storage means is eifective onlyduring that-pulse from the input ll circuit which reduces the enemy of i 1 storage' means to the extent required to effect initiation ofits recharging.

For a better understanding of the present invention, together with other and further objects thereof, reference is bad to the following descrlp 6 tion taken in connection with the accompanying a drawing and its scope will be pointed out in the appended claims.

In the accompanying drawing, Fig. 1 is a circuit diagram, partly schematic, of a frequency-divid 10' 'ing system embodying the present invention while Fig. 21s a group'of wave forms representing voltages developed at different points in the system of "Fig. 1 to aid in the understanding of the invention.

Referring now more particularly to the drawing, the system there illustrated comprises an impulse generator ID, a frequency-dividing mtem l I and a load circuit II, which may comprise an additional frequency-dividing system, con

,nected in cascade as shown. The generator "'20 may comprise any suitable generator or source of a periodieimpulse wave of a predetermined frequency. The system H comprises a voltagedividing system constructed in accordance with the present invention, while the system I! may be 25 of a.windingl-I constituting the secondary wind- 7 a ingof a feed-back transformer. The primary winding l8 of the transformer is included in the anode circuit of the tube It in series-witha source of operating potential, such as a battery ll. charging means are also provided for the condenser l I, operable only in response to, and during pulses of, the periodic input wave, for 7 the condenser II at the frequency of the input Q.

wave and to such extents that a predetermined number of the incremental discharges effect ini-- tiation .of the charging of the energy-storage means. This discharging means comprises a uniable tap on the battery I9, while the diode 20 is so biased as to maintain it nonconducting by virtue of the return of the input circuit of tube I6 to an adjustable tap on voltage divider I4.

An output or buifer tube 2 I is provided for the 10 dividing system H having its control grid and cathode connected to the corresponding elements of the tube I6 and thus, in effect, connected across the condenser I5. A series load resistor 22 is included in the anode circuit of the tube 2| and 25 the embodiment shown, is useful mainly to provide an independent output circuit whereby the wave developed by the system I I is of proper wave form as applied to the succeeding stage of the system.

30 The operation of the system of Fig. 1 may best be explained with reference to the curves of Fig. 2 which illustrate the wave forms of the volt- ,ages developed at various points in the system.

' a Each of curves AD, inclusive, represent voltage amplitude with respect to time. The wave developed in the output circuit of the generator Iii and appearing across the voltage-divider resistor I4, superimposed on the positive bias'derived from battery I9, is illustrated by curve A, being of a predetermined frequency and preferably of substantially rectangular-impulse wave form as shown. As it will presently appear, curves B and C represent the wave forms of the voltage developedbetween the upper side of the condenser I5 and ground and the voltage developed between the control grid of the tube It and ground, respectively, while curve D represents the voltage wave developed in the output circuit of the system II and applied to the system I2, which, in the pres- 5 ent case, is of a frequency one-seventh that of the input wave. I

Considering a cycle of operation of the system II as beginning at the pulse a, during which the condenser I5 is discharged to' a maximum extent 5 and the grid voltage of tube I 6 exceeds its cutoff value. Under this condition the tube I6 begins to pass current and, by virtue of the feedback windings I1 and I8, an induced positive voltage I crease in anode current and thus a regenerative effect which drives the control grid still more highly positive so that a large grid current flows 65 which is effective to charge the condenser I 5 to. its maximum negative value c. The decrease in' the. rate of change of anode current after-it reaches its maximum value-and the following re versal in its rate of' change produces a sharp induced negative voltagepulse d onthe control grid immediately following the regenerated .posi-Z tive pulse. This negative voltage pulse does not cause. any grid current to fiowin tube I6, so

that condenser. -I5is not discharged and re -Q' charged to an opposite polarity during this nega-v 75 tive pu1se.- Further, the anode circuit of the pulse b of curve C of. large amplitude is appliedto the control grid of the tube I6, causing an intube passes current only during'the high positive grid pulses when the resultant grid voltage exceeds the cutofl. point of the tube, as indicated in curve C.- The tube I6 is thereby biased below cutoff and again becomes nonconducting. The 5 means for charging condenser I5 is thus effective for charging the condenser only'during that pulse from the. impulse generator II) which reduces the energy of condenser I5 to a value sufficient to initiate the charging cycle. I 10 Since the diode is a unilaterally conductive device and is biased by means of the battery I9 so thatits cathode is normally positive relative to its anode, the negative charge developed on condenser I5 by the grid current 6f tube I6 nor- 15 mally cannot discharge therethrough. However, the negative pulses of the wave supplied by the generator II) are applied to the diode, by way of the voltage-divider resistor I4 and condenser I5 so as to overcome the normal diode bias, thereby rendering it conducting in response to each successive pulse of the'input wave, incrementally and periodically to discharge the condenser. The amplitude of the input wave pulses, as applied to the diode 20, are so controlled by adjustment of the voltage-divider resistor I4 and adjustment of the initial diode bias by means of the. adjustable tap on-the battery I9, and the time constant of the discharge circuit of the condenser I5, which includes diode 20, a portion of resistor I4, and a portion of source I 9, is made quite large relative to the duration of the applied pulses so that a single pulse is sumcient to effect only a predetermined partial or incremental discharge of the. condenser and a desired predetermined number of pulses are required to eflfect the discharge thereof to the value suflicient to raise the grid potential of the'tube I6 above the cutofi voltage at which the'tube I6 starts to pass current. For example; in the embodiment illus- 40 trated, six input pulses and consequent discharges of the condenser are insufllcient to raise the grid bias to cutoff, while the seventh pulse of a cycle tends to effect a discharge similar to the six preceding discharges, but due to the fact that it carries the grid bias beyond cutoff, this step is interrupted by a negative charging of'the condenser the partial or incremental discharges need not be equal in amplitude.

' The same voltage as is applied to the input electrodes of the tube IG'is applied to the input electrodes of the tube 2 I. This tube, being biased similarly to the tube I6, also passes current and repeats the input signal thereto only during the most positive pulses, so that there is developed in the output circuit of tube 2| a periodic wave comprising pulses, corresponding to the large I positive grid voltage pulses, at a frequency which is a fraction, in the present case is, one-seventh, of that of the input wave. The latter wave is applied, as explained above, to the load circuit I2 which may operate further to divide the frequen'cy in the same manner as the divider II or to utilize the wave-in any other desired manner.

While there has been described what is at pres- 55 ent considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in theappended claims to cover all such changes and modifications as-fall within the true spirit a'nd'scope of the invention.

. What is claimed is:

1 A frequency-dividing system comprising an 76 10 storage means at said predetermined frequency and to such extents that a predetermined number of said incremental discharges 'eflect initiation of said charging of said storage means, and an output circuit responsive to the successive charglngs oi said storage means; a

2. A frequency-dividing system comprising an input circuit adapted to be energized by a periodic wave of a predetermined frequency, energy-' storage means; charging means for effecting chargingof said storage 'meansonly upon its discharge to a predetermined value, unilaterally conductive discharging means for said storage means, means for maintaining said discharging means normally nonconductin'g, means coupling said discharging means to said input circuit for rendering said discharging means conducting only in response to and during pulses of said periodic, wave, incrementally and periodically to discharge said storage means at said predetermined irequency and to such extents that a, predetermined number of incremental discharges efiect' initiation of said charging of said storage means, and an output circuit responsive to the successive chargings of said storage means.-

3. A frequency-dividing system comprising an input circuit adapted to be energized by a periodic wave oi a predetermined frequency, energystorage means, charging means for effecting charging of said storage means only upon its discharge to a predetermined value, unilaterally 1 conductive discharging means for said storage means, means for maintaining said discharging means normally'nonconducting, means coupling said discharging means to said input circuit for rendering said discharging means conducting only in response to and during pulses of said periodic wave, incrementally and periodically to discharge said. storage means at said predetermined frequency and 'to such extents that a predetermined number of incremental discharges effect initiation of said charge, means for addustlng said coupling means to determine the number of said incremental. discharges sumcient to initiate said charging of said storage means,

and an output circuit responsive to the succes-;

v sive chargings of said storage means.

4. A frequency-dividing system comprising an input-circuit. adapted to be energized by a per-l odic wave or a predetermined frequency, energy-.

storage means, eharging means for eflfecting charging of said storage means only upon its discharge to a predetermined value, discharging means'for said storage means comprising a uni-v 5 laterally conductive device, means for biasing said device to maintain it normally nonconduct ing, means coupling said device to said input circu i-t forovercoming said bias and rendering said device conducting only in response to and during tents that a predetermined number oi. incremen tai discharges eflect initiationo! said charging- '15 or said storage means, and an output circuit'responsive to the successive chargings of said store means.

5. A frequency-dividing system comprising an input circuit adapted to be energized by a periodic wave of a predetermined frequency, a condenser, charging means for eflecting. charging of said condenser only upon its discharge to a predetermined value, discharging means for said condenser comprising a unilaterally conductive device connected in series with said condenser, means for biasing said deviceltp maintain it normally nonconducting, means coupling said device to said'input circuit for overcomingsaid bias and rendering such device conducting only in response to and during pulses of said periodic wave, incrementally and periodically to discharge said storage means at said predetermined frequency and to such extents that a predetermined number of incremental discharges effect initiation of said charging of said storage means, and an out-= put circuit responsive to the successive chargings of said condenser. I v

6. A frequency-dividing system comprising an input. circuit adapted to be energized by a periodic wave of a predetermined frequency, a condenser, charging means for efiecting charging of said condenser only upon its discharge to a predetermined value, discharging means for said condenser comprising a diode connected in series with said condenser, means for biasing said diode to render it normally nonconducting, means ecupling said diode to said input circuit for the'application oi said periodic wave thereto for peri-= odically overcoming said bias to discharge said condenser means incrementally at said prede termined frequency and to such extents that a predetermined number of incremental discharges effect initiation of said charging of said storage means, and an output circuit responsive to the successive chargings of said condenser.

E. Aireuuency-dividing system comprising an input circuit adapted to be energized by a periodic Wave of a predetermined frequency, a condenser, charging means for effecting charging oi said condenser only upon its discharge to a predetermined value. discharging means for said condenser comprising a diode connected in series with said condenser, means for biasing said diode torender it normally nonconducting, means cou-- pling said diode to said input circuit for the application of said periodic Wave thereto for periodically overcoming saidbias to discharge said condenser means incrementally at said predetermined frequency and to such extents that a predetermined number of incremental discharges effect initiation of said charge, means for adjusting said coupling means to determine the number i of said incremental discharges required toeflect i and an. output circuit responsive to thersuccesslve chargings 01 said condenser.

8. A frequency-dividing system comprising an input circuit adapted to be energized by a peri= odic 'wave of a predetermined frequency, a condenser, charging means for effecting charging of said condenser only uponits discharge to a predetermined value including a vacuum tube haying an input circuit including said condenser and anoutput circuit reactively coupled to said input circuit to charge said condenser only in a negative direction, discharging means for said condenser comprising a diode connected in series lit with said condenser, means for biasing said diode to render it normally nonconducting, means coupling said diode to said input circuit for the spplication of said periodic wave thereto for periodically overcoming said bias to discharge said condensermeans incrementally at said predetermined frequency and to such extents that a predetermined number of incremental dischargeseffect initiation of said charging of said storage means, and an output circuit responsive to the successive chargings of said condenser.

' 9. A frequency-dividing system comprising, an input circuit adapted to be energized by a periodic wave at a predetermined frequency, energy-storage means, discharging means for said storage meanscoupled --'to aid input circuit and operable only in response to and during pulses in said periodic'wave incrementally and periodically to, discharge said storage means at said predeterl mined frequency and to such extents that a predetermined number of said incremental dis- 5 

